Since May 2012, I have been investigating why some cities and regions have more start-up activity than others. My most surprising finding is that values matter more than almost any other factor. And the biggest surprise to me is that the most important of these values is the idea of giving back without expectation of immediate return.

Wharton's youngest-tenured and highest-rated professor, Adam Grant, published research showing that giving back without expectation of immediate return pays off. According to the New York Times, Grant observed that Harvard students who were selling ads for its “Let’s Go” travel books were much more effective when they heard a testimonial from a student whose scholarship was covered by their predecessors' ad sales.

Helping others without expectation of immediate return was highly motivating. A month after that testimonial, "Let's Go" workers boosted revenues by 171% and a later study calculated a 400% revenue boost brought in as a result of the testimonial. (Grant conducted studies that isolated that testimonial as the cause of the increased sales productivity.)

In my interviews with Silicon Valley start-up CEOs and investors, I found that this most productive Start-up Common operates on three values:

Give back without expectation of immediate return

Make risky bets on disruptive technologies targeting big markets

Keep learning by maintaining intellectual humility

As venture capitalist Mike Maples, Jr. explained to me last November, Silicon Valley's values derive from a philosophy of abundance. He said, "There are a lot of people in Silicon Valley who've already gotten rich, who try to help."

He continued, "When the primary goal is to create the pie or make the pie bigger, you don't first ask what's in it for you, you first ask how can I help accelerate something. So somebody comes to you and says, 'I got this idea, can you help me,' your first instinct is, 'How can I help,' not what's in it for me."

Why don't all cities share these values? The simple answer is that they have not enjoyed enough success to realize that giving back will make things better for everyone. For example, as Appcelerator CEO, Jeff Haynie explained to me last August, this feeling of giving back is absent from places like Atlanta, Haynie's home town.

As he explained, "Outside of Silicon Valley, I mean if you made it, you're on your boat and you're gone. The entrepreneurs that I know who 'made it' had zero social feeling that they need to help because they didn't get any help, they had to do it on their own, and by God, they're gonna maximize their energy somewhere else."

As I explained in an interview in Barcelona earlier this month, there are five other factors that are critical to an effectively functioning start-up common:

Pillar companies like Google that supply talent, a customer testing ground, and capital to start-ups;

Universities

Human capital

Investment capital

Mentoring -- both at the corporate and professional levels.

These factors interact to create cycles of start-up investment success that yield more capital and expertise that gets recycled into a region's start-up common. Even the failed start-ups get composted so that survivors can benefit from their resources.

But it all start with those values -- and Grant's work quantifies the benefits of giving back.